Stereoscopic apparatus



M y 7, 1940. c. n. MORIARTY STEREOSCOPIC APPARATUS Filedbec. 7. 1937 4Sheets-Sheet 1 Inventor Chafles D'Moriarbg.

IS Attorney;

c. b. MORIARTY smnnoscbrzc nrmxwus i'flid Dot}. 7, 1937 4 Sheets-Sheet 2mum "llli mmIII!IllllIIIIll|llIllIIIllIllllllllllllllllllllllllllIIIIlllllllllllllllllllllllllllllll|llllIIl|IlllllillllllllilfllllllIlllllllllllllllllllIlllllllhIf! lllllll Irv/enter: I Charles D. Mofl iarty,

's Abtofineg.

c. D. MORIARTY STEREO S CQPIC APPARATUS Filed D90 7, 1937 May 7, 1940.

4 Sheets-Sheet 3 Fig. 7.

' Inventor-z I Charles 1]. Mariam-t5,

b x f v His Atbovneg.

May 7, 1940.

C. D. MORIARTY S TEREOSCOPIG APPARATUS Filed Dec; 7, 1937 4 Sheets-Sheet4 E I Inventor: Charles D. Moviar'bg bu W7 HIS Attovneg.

. Patented 7, 1940 I s'raasoscorrc srrsna'ros Charles D. Moriarty,Schenectady, N. 1., asslgnor to General Electric Company, a corporationof New York Application December "I, 1937, Serial No. 178,584

8Claims.

The present invention relates to improvements in stereoscopic apparatus.

It is one object of the invention to provide improved means wherebyphotographs or other obs servations which are limited to two dimensionsmay be used to provide accurate measurements in a third dimension.

More specifically, it is my object to provide a stereoscopic apparatusof such character that two I" dimensional observations of an objectunder consideration may be translated by -mechanical means intomeasurements of such object in its third dimension. While not limitedthereto, the invention is primarily applicable in connection withradiographic (X-ray) studies of human bcdies. metal castings or otheropaque objects in which it is desired to observe and locate accuratelyforeign elements or defects.

The features of novelty which?! desire to protect herein will be pointedout with particularity in the appended claims. The invention itselftogether with further .obiects and advantages thereot may best beunderstood by reference to the following description taken in connectionwith the drawings-in which Fig. 1 shows in perspective the completeapparatus; Fig. 2 is an incomplete or partial section taken centrallythrough the apparatus; Fig. 3 is a plan view of the operative elementsof the apparatus; Fig. 4 :m is an enlarged detailed view of afragmentaryportion of Fig. 3; Fig. 5 is a fragmentary sectionalviewonlinel-iofl'ig4; Figs.6toarediagrammatic representations useful inexplaining the invention; Figs. 11 and 12 taken jointly, :n comprise arepresentation ofa measuring device which comprises an important featureof the invention; Fig. 13 is a view on line l3--i3 of Fig. 11; Fig. 14is aview online "-44 of Fig. 11; Fig. 15 is a view on line lF-il of Fig.12 and Fig. 16 is m a more or less -tic view illustrating one mode ofuse of the measuring device of Fig. 11. v

Referringtol'imlitwillbeseenthatihe apparatus includes an elongatedtable II. supported at its opposite ends by cooperating uprights I! andit. Means. (not shown) may be provided for raising and lowering thetable to inner part II (shown more clearly in Fig. 3) is suspended fromthe guide rails II and it by means of supporting brackets 23. A mirrorIt, arranged normally to the. plane of the table, rests on the uppersurface of the frame 20 and is I supported laterally by means of blocks2' which are slidably mounted on the guide rails l5 and it. Themirror isshown as being clamped to the frame 20, by means of thumb screws 21 and28, but it is contemplated that these may be loosened 10 when occasionrequires to pemiit removal of the mirror.

The function of the table iii and its relation to the other parts of theapparatus may best be understood by reference to Fig. 2 which shows asection taken through the table in the region of themirror 24.Fromthisviewitwillbeseen that the table comprises a hollow structurewhich is closed at-the top by means of a hinged cover including a plateof translucent motel-m 20' such so as glass. Within the confines of thetable there are provided one or more light sources illustrated aselectric lamps 3|. These serve to throw light v upwardly through theplate it and to illuminate photographs or other pictorialrepresentations 25 supported on the surface of the table. (In onecontemplated use of the apparatus, such representations may comprisepically related X-ray photographs of a subject desired to be studiedradiographically.) Another transparent plate 20, covering only a portionof the table area, may be laid on the surface of the plate 28' foranchoring and flattening the pictures to be viewed.

It is one hmction of the apparatus so-far deas scribed to enable anobject under consideration to be vbwedstereoscoplcally. To thisend,'stererelatedviewsof theobiectmaybe supported on the upper surfaceof the table II of-the mirror it as indicated at 40 -3landl2in'1'lg.3.Asappears fromthisflgure,

these views are arranged symmetrically on oppositesidesofthemirrorbutaresopositionedas to face in opposite directions;that is, that portionoftheimagewhichisontheleftinoneview 46 is on theright in the other view. Shades or screens and flwhiehareprovided inconnection with theupper surface of the tablemay bedrawntosnchapositionastoframethepictures under consideration andtoconcentrate thelight 50 n:; The positionoftheseshadesmaybecontrolledby meam-ot handles 38 and I. which areslidable onaguiderail I1. 7 V

Liftheeyes ofan IQ observer are positioned with respect to the mirror 24as indicated at 39 (or alternatively adjacent to the opposite side ofthe mirror), a stereoscopic image of the object under consideration maybe obtained. This may best be understood by reference to thediagrammatic representation of Fig. 6 in which the relation of themirror 24 to the two stereoscopically related views 3| and 32 is shownas seen from the side. The eyes of an observer are indicated at 43 and44 respectively. It is assumed that the views 3| and 32 each include thepicture or outline of an object desired to be viewed stereoscopically,say, the picture of a small round object such as a spherical shot. Thesepictures are indicated in the relation which they are assumed to occupyin the views as a whole at'D' and D" respectively.

If the line of vision of the observer is directed toward the right itwill be seen that the picture D will be viewed directly by the right eye44, as indicated by the solid line rays d. The picture D" on the otherhand will be viewed by the left eye as a reflection in the mirror 24,the manner in which this picture is received by the eye being indicatedby the solid line rays d". Due to an optical illusion, however, theobserver will have the impression of seeing, not the picture D", butinstead a virtual pictureD' adjacent to but displaced from the pictureD. (The displacement is a result of the stereoscopic relation betweenthe two views 3| and 32.)

The effect produced on the observer by this simultaneous observation oftwo displaced images is to create the illusion of a composite imageexisting at D, the region of intersection of the rays d and (1''. By aphenomenon which is familiar to most persons", this stereoscopic imageappears to be solid and to have extension in a. third dimension. It canbe readily shown that the apparent position in space of the stereoscopicimage D is a function of the displacement between the pictures D and Dand consequently of the respective spacings of the pictures D and D'with. respect to the mirror 24. This is a fact which isv utilized in thefurther aspects of the invention.

In addition to providing a stereoscopic image of an object underconsideration, it is a further important function of my invention toprovide means for producing an indexing image which is capable ofapparent motion in three dimensions so that it may act as a pointer withrespect to any particular part of the object which is desired to beespecially examined. Referring again to Fig. 3, one form of indexingmeans is shown as comprising'a pair of similar indexing elements 50 and5| (preferably although not necessarily hairlines) positioned onopposite sides of the mirror 24 and each associated with one of thepictorial representations 3| and 32. These indexing elements orhairlines are so mounted as to be movable convergently toward ordivergently .away from the mirror 24 or to be movable simultaneously ina common direction with respect to the mirror. They may be viewedstereoscopically by means of the mirror 24 to provide a common indexingimage having a desired optical relationto the object image.

Referring again to Fig. 6 it will be'seen that from the standpoint of anobserver the hairline 5| is viewed directly along the ray 1), and thehairline 50 is viewed indirectly by reflection as indicated by the rayb". A virtual image of the latter hairline will also be seen incoincidence with the hairline 5| as indicated by the ray 12",

and the effect of a stereoscopic image will be obtained. With theparticular hairline positions selected, this stereoscopic image willappear to coincide with the surface of the photograph 32, due to theintersection of the rays b and b at such surface.

The effect of simultaneously moving the hairlines 50 and 5| convergentlytoward the mirror 24 is shown in Fig. 7 in which both hairlines arenearer to the mirror than in Fig. 6. From a comparison of these figuresit appears that as long as this motion is symmetrical, that is, as longas each hairline is moved neither more nor less than the other hairline,the hairline image will remain in the same horizontal plane. It willhowever, move in a direction transverse to the line of vision; that isto say, parallel to the surface on which the views 3| and 32 aresupported. In the position shown in Fig. 7 the hairline image wouldappear to the observer to be directly behind the object image D.

The effect of moving the hairlines 50 and 5| simultaneously in the samedirection (i. e. to the right or left) is shown in Fig. 8 in which thehairlines are represented as having each been shifted slightly to theleft from the positions whichathey occupy in Fig. 7. The effect of theparticular extent of motion indicated issuch as to bring the hairlinesinto substantial coincidence with the stereoptically related views D'and D" of the object D. Consequently the composite image of thehairlines must necessarily appear to coincide spatially with the objectimage D. In other words. the hairline image has apparently been causedto move in a third dimension, that is,.

in a direction parallel to the line of vision.

If the hairlines are now again moved symmetri cally so as to convergetoward the mirror 24 in the manner described in connection with Fig. 7,further motion of their image in a plane transverse to the line ofvision will occur. As appears in Fig, 9, such symmetrical hairlinemotion will not produce displacement of the hairline image parallel tothe line of vision, but will cause it to scan a plane 38 parallel to thesurface of support of the views 3| and 32. I

The practical importance of the facts just described consists in thefact that the observer or operator can voluntarily control the positionof the hairline image to cause it to coincide precisely with theapparent position of the object image, no matter where such image maybe. By means which will be hereinafter described the steps taken inproducing such coincidence can also be made to furnish desiredmeasurements with respect to the object under consideration.

For causing apparent motion of the hairline image in a directiontransverse to the observers line of vision there is provided means foreffecting simultaneous and symmetrical motion of the hairlines withrespect to the mirror 24. Such means may comprise, for example, acontinuous flexible cable or cord 60 (Figs. 3 and 4) which runs overpulleys. 6| arranged at the corners of the frame 2| and supported. onsuch frame. "A spring-pressed take-up roll 6| serves to maintain thecable under tension. It will be clear with the arrangement illustratedthat if certain portions of the cable 60 are caused to move to areadapted to travel in the same direction and by attaching the ends of thehairline 5| to parts of the cable which are adapted to move in theopposite direction. Thus, at the side of the frame 2| nearest to theobserver in mg. 1, the inner strand of the cable is attached to thehairline and the outer strand to the hairline ll. At the far sidev ofthe frame the order of attachment is reversed.

v A possible mode of connecting the hairlines to the cable 80 is shownin Fig. 5 which represents a section taken on line 5-4 of Fig. 4. Inthis figure it appears that the hairline 50 is secured to the dependentend of an element 82 which forms part of a clamp fixedly engaging thecable 80. The other part of this clamp is formed integrally with anoutwardly extending handle 63 which is adapted to be manipulated by theoperator. A longitudinally extending slot 84 formed in the frame 2| (seeFig. 4) permits the clamp to be moved to the right or left whileconfining its motion to the proper plane. A slot 65 formed in the frame20 (Fig. 1) also permits unobstructed lengthwise motion of the handle68. Referring to Fig. 3 it is apparent that such motion necessarilyproduces simultaneous conver gent or divergent movement of the hairlines5|! and 5|. As previously explained, the effect of this simultaneousmotion is to cause the hairline image to appear to move in a planetransverse to the observer's line of vision.

Simultaneous motion of the hairlines 50 and 5| in a. common direction iseffected by moving the frame 2| on which they are both mounted. As isshown clearly in Fig. 3, this frame is movably supported from the outerframe 20 so as to make this motion possible. The supporting force on theframe (see F18. 15).

It has already been pointed out that motion of the hairlines 50 and 5|in a single direction l serves to cause their common image to appear toof a part movable with and in accordance with the motion of the frame IIand a stationary part adapted to provide measurements in accordance withsuch motion. These elements are shown in detail in Figs. 11 and 12.

Prior to describing the measuring means fully, it is desirable toconsider in some detail the conditions under which stereoscopicallyrelated views are' initially obtained. 'In Fig. 10 I have illustrated anarrangement conventionally employed in obtaining stereoscopicallyrelated X-ray photographs for use in the examination of opaque bodiessuch as castings. In this figure the ob- Ject of study is represented atIt and is assumed to have embodied therein a defect, indicated at G,which it is desired'to discover and locate precisely. To this end theobie tllis supported above a film supporting surface I! adapted toreceive a film which is sensitive to the action of X-rays.. With thefilm in place, a first radiograph is taken by means of x-rays projectedfrom an x-ray tube, the target of which is illustrated at I3.Thereafter, the exposed film is removed and another similar filmsubstituted in its place. A second picture is then obtained by the useof another X-ray source 14 displaced from the first by a distance A. g

It is apparent that with the conditions illustrated, the firstradiograph obtained will embody a picture of the defect G at a point Gdetermined by the projection of rays of X-light 15 proceeding from thetarget I3 through the defect G onto the film surface. Similarly, thesecond radiograph will include a picture of the defeet at point G" asdetermined by a projection of a ray of x-light I5 proceeding from thetarget 14 through the defect. The displacement Vg between these twopictures which would be noted if the respective radiographs weresuperimposed is obviously a function of the tube shift A; of B, thetube-film distance; of C, the object-film distance; and of X, theunknown height of the defect G. As a matter of fact, this relationshipcan be expressed mathematically by the equation Since A, B andC areconstants and are presumably known to the operator the quantity X can bereadily computed once V; is known. It is an important feature of myinvention that it combines optical means for determining V; with meansdependent on such determination for computing mechanically the value ofX. Exemplary instrumentalities by which this result may be.

accomplished are shown in Figs. 11 and 12. The elements of these figureswill first be described structurally in detail and then with referenceto their function and operation.

' As previously suggested the measuring means comprises a stationarypart or parts and a part which is movable in accordance with the motionof the hairlines l0 and SI. The stationary part includes in the firstinstance a scale I6 which is mounted in fixed relation on one end of thestationary frame 20. Adjacent to the upper end of this scale there isshown a second scale 11 which is at right angles thereto. At itslefthand end the second scale is formed integrally with a slotted member18 which is adapted to interfit with and slide on the scale 16 (see Fig.13). Adjacent the lowerend of the scale 16 there is shown a third scale.0 which is also so mounted as to be slidable longitudinally of .thescale 16. Cutting across the face of the scale 80 there is shown anindex line which is illustrated as comprising a thread 83 but which mayalternatively comprise the edge of a thicker member such as a rodor-bar. The upper end of the thread is adjustably secured to the scale Hby means of a rider .4 adapted to move along such scale. The position ofthis thread end (i. e. its spacina from the center line of the .scale16) may be ascertained by a reading obtained through a slot 85 appearingin the rider, which slot serves to make visible anarrow portion of thescale 11. The markings on the various scales are in linear units andshould, for convenience, be in. the same units on all scales.

At its lower end, the index member or thread 83 is wound on a springdriven drum .8 by means of which it is maintained under tension andbiased against a. stud or projection 86 (see Fig. 15) projectingupwardly from a member 81. This, in turn, is connected to the frame 2|so that when the frame is moved to the right or left under the action ofthethumb screw 88, the thread 83 is caused to travel across the face ofthe scale 80.

The mode of cooperation of the measuring device and the stereoscopicapparatus may best be understood by referring to the manner in whichthe'former is used. Assuming the existence of two stereoscopicallyrelated views (photographs) of an object desired to be studied, it isnecessary to "calibrate the measuring device by setting up on itsvarious scales, the known conditions under which the views wereobtained. Thus, if a radiographic process such as that described inconnection with Fig. 10 is involved, the position of the rider 84 isadjusted along the scale until the value read through the slot is equalto the tube shift A (Fig. 10). The scale 11 is then moved as a wholealong the scale 16 until its height as read on such scale corresponds tothe known tube-to-film distance B. Finally the scale 80 is raised orlowered until its zero point is at a point on the scale 16 correspondingto the object-to-film distance C. I

In order to assure proper correlation of the viewing apparatus and themeasuring device, the latter is seton zero by turning the thumb screwuntil the index thread 83 cuts the zero point 90 of the scale 80. If theapparatus is now properly adjusted, this should indicate a coincidenceof the hairline image with the bottom plane of the object image. Thiscondition may or may not be actually fulfilled, and ii" it is not, itwill be necessary to make a further adjustment.

Such further adjustment is accomplished by moving the mirror 24 to theleft or right by sliding the blocks 26. Since the mirror is more or lessrigidly joined to the frame 20, this latter member also moves, carryingwith it the inner frame 2| and the hairlines 50 and 5!. Consequently,the apparent position of the hairline image as received in the mirror isnot affected.

The pictures 3| and '32, on the other hand, remain stationary since theyare supported independently of the frames. The resultant relative motionof the mirror and pictures causes apparent motion of the object image ina direction parallel to the observers line of vision. By properadjustment of the mirror this image can be caused to reach a positionwhere its bottom plane appears to coincide with the hairline imagethisbeing the condition desired to be attained.

In order to facilitate the adjustment Just referred to, it is convenientto have some readily identifiable index element associated with thebottom plane of the object under consideration. In the case ofradiographic studies this may suitably comprise a lead shot or otherdense body embedded in the lower surface of the object as indicated at Din Fig. 10. If this is the expedient actually employed, the condition ofthe measuring device of Figs. 11 and 12 after the adjustments justdescribed will provide a geometric arrangement exactly similar to thatformed by the ray l5 and the dotted ray 96 in Fig. 10. That is to say,the intersection of the thread 88 with the center line of the scale 88(Fig. 12) will simulate the intersection of the ray 96 (Fig. 10) withthe ray 15 at the bottom plane of the object III. (The zero lineof thescale 88 represents the bottom plane of the object.)

If the thumb screw 68 is now turned in such a way as to move the frame2| to the left the lower end of the thread 83 will move with it and thepoint of intersection of the thread and the center line of scale 88 willmove up on the scale.

If the apparatus is to operate in the desired manner, the hairline imageof the stereoscopic apparatus should come into coincidence with theimage of the defect G at the instant that the reading of scale 80 issuch as to indicate the location of such defect (that is, the distance Xof Fig. 10) That this desired condition will necessarily be fulfilledmay best be understood by a further consideration of Fig. 8.

As has already been explained in connection with that figure,coincidence of the hairline image with the image of any specified objectoccurs when the displacement between the directly viewed hairline 5| andthe virtual" hairline 50' is precisely the same as the displacementbetween the directly viewed picture and the virtual picture of thatobject (This is the condition which is actually fulfilled in Fig. 8). Inthe event of a zero reading of the scale 80, the displacement of thereal and virtual hairlines corresponds (after proper adjustment of theap-- paratus) to the displacement of the real and virtual pictures D andD' of any representative element (say, a lead shot) in the bottom planeof the object under consideration. If this element corresponds to theelement D of Fig. 10, it can be shown that the hairline displacement inquestion is necessarily equal to the distance Va (since Va actuallyrepresents the stereoscopic displacement of the two radiographicpictures of D).

The effect of shifting both hairlines without changing their relativespacing is to increase the apparent displacement between the real andvirtual hairlines (this is illustrated by the contrast between Figs. 7and 8). Furthermore, due

. to the doubling effect of the mirror, a given amount of hairline shiftwill produce precisely twice that amount of change in displacementbetween the real and virtual hairline images. This also may be seen bycomparison between Figs. 7 and 8.

Referring to a particular case, if both hairlines are moved to the leftby motion of the frame 2|, the hairline 50 may be brought to position5012 where it is in alignment with the object picture G". By symmetry,the virtual hairline 58' will also move to 50'a into alignment with thevirtual object picture G. Consequently, the hairline image will becomecoincident with the object image G. (G is considered to be the defectrepresented in Fig. 10.)

The resultant change in the distance between the hairline 5| and thevirtual hairline 50' is equal to the difference between the distance Vgand the distance Va (Fig. 10) However, the actual amount of hairlineshift (as produced by moving frame 2|) is equal to one-half thedifference between V; and Va. (This is another consequence of the motiondoubling effect of the mirror 24). In order that this, factor shall notprevent the true operation of the measuring device it is necessary thatall the elements of this device be half scale. That is to say, thevarious scales I6, 11, and 80 should be given lengths precisely halfthose which they are supposed to represent.

With this condition fulfilled, since any motion of the frame 2| impartsa similar motion of the bottom end of the indexing thread 83, it isclear that after the shift just referred to the arrangement of thethread and the center line of the scale 18 must duplicate thegeometrical pattern made by the rays I5 and 15' of Fig. 10. That is tosay,

to B, and the distance between the aero points of the scales I! and llto C. the displacement of the lower end of the thread I! from the zeropoint of the scale It must, after the adjustment lust described,correspond to the quantity)! of Fig. 10. Finally by the principle ofsimilar triangles, the reading of the scale 80 (i. e. the distance fromits zero point to the point of intersection of its center line with thethread 83) must correspond to the distance X which it is desired todetermine.

Summarizing then, the use of the apparatus in analyzing stereoscopicallyrelated views consists in the following steps: The various scales of themeasuring device are set to simulate the spatial conditions under whichthe views were obtained; next the thumb screw 68 is turned to provide azero reading of the scale 80 as determined by the position of the thread83, and the mirror 24 is adjusted so that such zero reading correspondsto coincidence of the hairline image seen by the observer with the imageof some point at the bottom plane of the object under consideration.Thereafter, the thumb screw '8 is further adjusted to bring the hairlineimage into coincidence with the image of the defect desired to belocated. This will result in a reading of the scale 80, determinative ofthe location of the defect.

It should 'be noted at this point that a correct reading of the scaleill will be obtained even though the hairline image does not coincidewith the defect image as long as it does fall in the same horizontalplane as that image. Complete coincidence of the two images may beobtained in order to improve the accuracy of the operator's judgment byproducing a convergent or divergent motion of the hairlines (byadjustment of the handle 83) to cause apparent motion of their image ina direction transverse to the line of vision.

It should be clearly understood that this operation has nothing to dowith the functioning of themeasuring device but simply makes it easierfor the operator to determine when the hairline image is on the sameapparent level (i. e. in the same horizontal plane) as the defect image.

I have found that the scale Ii-must be of an inconveniently great lengthif it is to be adopted for registering the values of the quantity 3which are frequently encountered in actual practice. I have, therefore,provided means for obtaining the elect of a relatively great extensionof such scale without actually requiring any physical extension uppersurface of the rider should be in the form I of a smooth are having aradius of curvature linearly equal to the scale extension desired to beobtained. Whenthe conditions are such that the extendedportion of thescale is to be used, the upper end of the thread I! is rendered freelymovable with respect to the rider by the use of a bearing element Illadapted to roll in a groove provided'forv that purpose in the ridersurface.-

Thls feature is illustrated clearly in Fig. 14 in a which '4 is therider and III is the rolling element.

From a consideration of Fig. 16, it will be seen that with the elementill free to move over the surface of the rider, the thread will, as longas it is under tension, seek a position-in which it 1.8

normal to them which forms such altos.

Furthermore the direction line of the thread will,

, if extended, pass through the center of generation I of the arc. Theresultant effect-is thus precisely the same as though the upper end ofthe thread were fixedly attached at 0, and the motion of the thread 83with respect to the scale II will 'be the same as though this conditionwere ful- As long as the actual (unextended) length of the scale 16 issuflicient to permit the distance B to be duplicated thereon, therolling element I00 is immovably secured to the rider 84 by means of aspring clip I02 adapted to receive and retain the same. with thisarrangement the readings of the left-hand side of the scale 18 areutilized. However, when a greater scale length is required, the rollingelement Hill is released and the scale readings to the right of thecenter line of scale 16 are used. By means of these alternative modes ofuse the flexibility of the apparatus is greatly increased.

Although I have described my invention in connection with radio'graphicanalysis, it is also applicable in connection with the preparation ofcontour maps from stereoscopically' related aerial photographs. In thislatter use the quantities which must be known comprise the height of theplane from which the photographs are taken, the distance traversedbetween photographs and the height of some one point appearing in thephotographs.

In using these data the first quantity (plane height) is set up on thescale I6; the second (camera shift) is set up on the scale 11, and thethird is used to calibrate the apparatus in accordance with the zerosetting operation previously described. The intermediate scale 80 neednot be employed since all height values will be measured from a commonreference (ordinarily sea level). In other words, no quantitycorresponding to the object-film distance C (Fi 10) will be involved.

While I have in the foregoing described a particular structuralembodiment, it will be understood that many modifications may be made bythose skilled in the art without departing from the invention. I,therefore, aim in the appended claims to cover all such variations ofstructure and use as come within the true spirit and scope of theforegoing disclosure.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

l. A sterewccpic apparatus comprising a refiecting member providing asubstantially plane reflecting surface, means for supporting a pair ofstereoscopically related views on opposite sides of said member and inplanes transverse thereto,

a pair of similar indexing elements, each arranged to be associated withone of said views during the use'of the apparatus and each adapted formotion parallel to the plane of its associated view, and means operableto produce simultaneous divergent or convergent motion of theindexingelements with respect to the reflecting member or alternatively to movethe elements simultaneously in a single direction with respect 1 to suchmember.

2. A stereoscopic apparatus comprising means providing a substantiallyplane reflecting surface arranged to be viewed grazingly by an observer.

means for supporting a pair of stercoscopicaliy related views of anobject to be investigated on opposite sides of said surface and inplanes transverse thereto, the mode of support being such that 'by theaid of the reflecting surface the use of the apparatus and each adaptedfor motion parallellto the plane of support of its associated view, theelements also being so positioned that they may be viewed simultaneouslyby the aid of the reflecting surface to provide a single stereoscopicimage thereof, means for simultaneously moving the indexing elementsconvergently toward or divergently away from the reflecting surface tocause apparent motion of their common image in a plane transverse to theobservers line of vision and means for simultaneously moving the membersin a single direction to cause apparent motion of their image in a planeparallel to the line of vision.

3. A stereoscopic apparatus comprising a table or frame for supportingin a single plane a pair of stereoscopically related views of an objectto be studied, .a mirror supported between such views and having itsreflecting surface in a plane substantially normal to their plane ofsupport, a pair of hairlines arranged on opposite sides of the mirrorand in parallelism with its reflecting surface, each of said hairlinesbeing arranged for motion over the surface of one of saidstereoscopically related views, means for simultaneously moving thehairlines convergently toward or divergently away from the mirror, andmeans for moving the hairlines simultaneously in a common directionwithout disturbing the spatial relationship between them.

4. A stereoscopic apparatus comprising means 7 providing a substantiallyplane reflecting surface, means for supporting a pair of two dimensionalviews of an object to be investigated on opposite sides of said surfaceand in planes transverse thereto, the mode of support being such that bythe aid of the reflecting surface the views may be observedsimultaneously so as to afford an image of the object having apparentextension in a third dimension, a pair of similar indexing elements eacharranged to be associated with one of said views during the use of' theapparatus and each adapted for motion parallel to the plane of supportof its associated view, the elements also being so positioned that theymay be viewed simultaneously by the aid of the reflecting surface toprovide a single stereoscopic image thereof, means for simultaneouslymoving the members in a single direction to cause apparent motion oftheir image in said third dimension and means including a partadjustable in accordance with the-motion of said elements forinterpreting the apparent position of their image in terms of truemeasurements in said third dimension.

5. A stereoscopic apparatus comprising means providing a substantiallyplane reflecting surface, means for supporting a pair ofstereoscopically related views of an object to be investigated onopposite sides of said surface and in planes transverse thereto, themode of support being such that by the aid of the reflecting surface theviews may be observed simultaneously so as to afford a single image ofthe object having apparent extension in a third dimension, a pair ofhairlines arranged on opposite sides of said reflecting surface so thatby the aid of said surface they may be viewed simultaneously to providea single stereoscopic image thereof, each hairline being associated withone of said views and being adapted for motion parallel to the plane ofsupport of its associated view, a movable frame supporting both of thehairlines, means associated with the frame for simultaneously moving thehairlines convergently towards or divergently away from the reflectingsurface to cause apparent motion of their common image in a planetransverse to the observers line of vision, means for moving the frameand hairlines to cause apparent motion of the hairline image in saidthird dimension, and means dependent on the motion of the frame forinterpreting the apparent position of thehairline image in terms of truemeasurements in said third dimension.

6. In combination, a stereoscopic apparatus of the type which employs apair of two-dimensional views of an object under investigation toprovide an image of the object which has apparent extension in a thirddimension, means including a pair of similar indexing elementsassociated with the apparatus for providing a stereoscopic indexingimage whichv has a desired optical relation to the object image, meansfor moving the elements to produce apparent motion of the indexing imagein said third dimension, and means for mechanically and automaticallyinterpreting the apparent position of said indexing image in terms oftrue measurements in said third dimension, said last named meansincluding a scale-bearing member whereon such measurements may be readdirectly, an indicating member cooperating with said scale-bearingmember, calibrating means for adjusting the relative positions of saidmembers in accordance with the conditions, both of angle and distance,under which the said two-dimensional views of the object were taken, anda connection between one of said members and the means employed formoving the said indexing elements, said connection being effective tochange the positional relationship of the said scale-bearing andindicating members in accordance with the motion of said indexingelements.

'7. In combination, a stereoscopic apparatus of the type which employs apair of two-dimensional views of an object under investigation toprovide an image of the object which .has apparent extension in a thirddimension, means including a pair of similar indexing elementsassociated with the apparatus for providing a stereoscopic indexingimage which has a desired optical relation to the object image, meansfor moving the elements to produce apparent motion of the indexing imagein said third dimension, and means for mechanically and automaticallyinterpreting the apparent position of said indexing image in terms oftrue measurements in said third dimension, said last named meansincluding a scale-bearing member whereon such measurements may bereaddirectly, an indicating member cooperating with said scale-bearingmember, a plurality of auxiliary scales associated with saidscale-bearing member for preliminarily adjusting the relative positionsof said members in accordance with .the conditions both of angle anddistance under which the said two dimensional views of the object weretaken, and a connection between one of said members and the meansemployed for moving the said indexing elements, said connection beingefiective to change the positional relationship of the said associatedwith the apparatus for providing a stereoscopic indexing image which hasa desired optical relation to the object image, means for moving theelements to produce apparent motion of the indexing image in .saidthirddimension, a scale-bearing member associated with the apparatus, amovable member providing a reference line angularly intersecting thescale of said first named member, calibrating means for preliminarilyadjusting the angular relationship and point of intersection of the lineand scale in accordance with the conditions of angle and distance underwhich the said two-dimensional views of the object were taken, and amechanical connection between the said movable member and the meansemployed for moving the indexing elements, said connection beingefiective to change the positional relationship of said scale andreference line in accordance with the motion of the indexing elementsthereby to interpret the apparent position of said indexing image interms oi true measurements in said third dimen- 10 sion.

7 CHARLES D. MOBIARTY.

